This invention relates, in general, to exposure control mechanisms and, in particular, tape-like blades which are driven, preferably, electromagnetically.
Heretofore, a variety of blade mechanisms have been proposed for use in controlling scene light along an optical path. With the advent of miniature cameras and with the desire to program shutter blade movement, it becomes highly advantageous to reduce, even more, the size and weight of the shutter mechanism components. Towards this end it is desirable to have the blades relatively light in weight so as to facilitate acceleration thereof from zero to desired speed. Additionally, it is desirable to have the blades move as silently as possible and be simple and inexpensive to manufacture. Moreover, while possessing the above characteristics, the blades should be sufficiently strong and yet not be too resistant to bending so as to be able to pass over rollers or the like.
However, with very thin blades the strength, durability and light proofness thereof are lessened. There are additional drawbacks with blades made of such thin material. One major problem is the fact that the thinner the material is the more difficult it is to move without causing folds in the blade during advancement of the latter. This is especially true when the blades are being pushed along their path of travel and encounter sliding friction. Several suggestions have been put forth to prevent this uncontrolled bending or bowing of the blade. One, for instance, is disclosed in U.S. Pat. No. 3,685,423 which suggests the use of flat plastic foils which have corrugated surfaces which are at right angles to the direction of blade travel. As a result, the shutter blade possesses sufficient resistance to bending in a direction generally perpendicular to its direction of travel. A difficulty with using corrugations or grooves to obtain optimal mechanical strength is that there must be a fairly precise distribution of the grooves as well as appropriate sizes thereof for the shutter blade to perform optimally.